System and print head for continuously manufacturing composite structure

ABSTRACT

A print head is disclosed for use with an additive manufacturing system. The print head may include a matrix reservoir configured to hold a supply of matrix, and a flop guide located within the matrix reservoir. The flop guide may be configured to at least partially surround a continuous reinforcement passing through the matrix reservoir. The print head may also include a nozzle connected to an end of the matrix reservoir downstream of the flop guide.

RELATED APPLICATIONS

This application is based on and claims the benefit of priority fromU.S. Provisional Application No. 62/611,922 that was filed on Dec. 29,2017, the contents of which are expressly incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates generally to a manufacturing system andprint head, and more particularly, to a system and print head forcontinuously manufacturing composite structures.

BACKGROUND

Extrusion manufacturing is a known process for producing continuousstructures. During extrusion manufacturing, a liquid matrix (e.g., athermoset resin or a heated thermoplastic) is pushed through a diehaving a desired cross-sectional shape and size. The material, uponexiting the die, cures and hardens into a final form. In someapplications, UV light and/or ultrasonic vibrations are used to speedthe cure of the liquid matrix as it exits the die. The structuresproduced by the extrusion manufacturing process may have any continuouslength, with a straight or curved profile, a consistent cross-sectionalshape, and smooth surface finishes. Although extrusion manufacturing canbe an efficient way to continuously manufacture structures, theresulting structures may lack the strength required for someapplications.

Pultrusion manufacturing is a known process for producing high-strengthstructures. During pultrusion manufacturing, individual fiber strands,braids of strands, and/or woven fabrics are coated with or otherwiseimpregnated with a liquid matrix (e.g., a thermoset resin or a heatedthermoplastic) and pulled through a stationary die where the liquidmatrix cures and hardens into a final form. As with extrusionmanufacturing, UV light and/or ultrasonic vibrations are used in somepultrusion applications to speed the cure of the liquid matrix as itexits the die. The structures produced by the pultrusion manufacturingprocess have many of the same attributes of extruded structures, as wellas increased strength due to the integrated fibers. Although pultrusionmanufacturing can be used to continuously manufacture high-strengthstructures, the resulting structures may lack the form (shape, size,precision, and/or surface texture) required for some applications. Inaddition, conventional pultrusion manufacturing may lack precise controlover curing and the ability to dynamically change materials in thecomposite material during manufacture. Further, the variety of patternsand shapes integrated within the pultruded structures may be limited,thereby limiting available characteristics of the resulting structures.

Continuous fiber 3D printing (a.k.a., CF3D™) has recently been developedto address the shortcomings of extrusion and pultrusion manufacturing.CF3D involves the use of continuous fibers embedded within a matrixdischarging from a moveable print head. The matrix can be a traditionalthermoplastic, a powdered metal, a liquid resin (e.g., a UV curableand/or two-part resin), or a combination of any of these and other knownmatrixes. Upon exiting the print head, a head-mounted cure enhancer(e.g., a UV light, an ultrasonic emitter, a heat source, a catalystsupply, etc.) is activated to initiate and/or complete curing of thematrix. This curing occurs almost immediately, allowing for unsupportedstructures to be fabricated in free space. When fibers, particularlycontinuous fibers, are embedded within the structure, a strength of thestructure may be multiplied beyond the matrix-dependent strength. Anexample of this technology is disclosed in U.S. Pat. No. 9,511,543,which issued to TYLER on Dec. 6, 2016 (“the '543 patent”).

Although CF3D™ provides for increased strength, compared tomanufacturing processes that do not utilize continuous fiberreinforcement, improvements can be made to the structure and/oroperation of existing systems. The disclosed additive manufacturingsystem and print head are uniquely configured to provide theseimprovements and/or to address other issues of the prior art.

The disclosed system is directed to addressing one or more of theproblems set forth above and/or other problems of the prior art.

SUMMARY

In one aspect, the present disclosure is directed to a print head for anadditive manufacturing system. This print head may include a matrixreservoir configured to hold a supply of matrix, and a flop guidelocated within the matrix reservoir. The flop guide may be configured toat least partially surround a continuous reinforcement passing throughthe matrix reservoir. The print head may also include a nozzle connectedto an end of the matrix reservoir downstream of the flop guide.

In another aspect, the present disclosure is directed to a system foradditively manufacturing a composite structure. The system may include ahead configured to discharge a continuous reinforcement that is at leastpartially coated with a matrix. The head may include a matrix reservoir,a flop guide located within the matrix reservoir and at least partiallysurrounding the continuous reinforcement, and a nozzle connected to anend of the matrix reservoir downstream of the flop guide. The system mayalso include a support configured to move the head during discharging.The flop guide is configured to maintain a path of the continuousreinforcement passing through the matrix in the matrix reservoir duringtilting of the head by the support.

In yet another aspect, the present disclosure is directed to a method ofadditively manufacturing a composite structure. The method may includedirecting a continuous reinforcement through a matrix reservoir insideof a print head to wet the continuous fiber with a matrix. The methodmay also include discharging the matrix-wetted continuous fiber througha nozzle of the print head, and tilting the print head duringdischarging. The method may further include deflecting the continuousfiber within the matrix reservoir away from an axial trajectory tosubmerge the continuous fiber in the matrix during tilting of the printhead.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an exemplary disclosed additivemanufacturing system; and

FIGS. 2 and 3 are cross-sectional illustrations of an exemplarydisclosed print head that may be used in conjunction with the system ofFIG. 1.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary system 10, which may be used tocontinuously manufacture composite structures 12 having any desiredcross-sectional shape (e.g., circular, rectangular, or polygonal).System 10 may include at least a support 14 and a head 16. Head 16 maybe coupled to and moved by support 14. In the disclosed embodiment ofFIG. 1, support 14 is a robotic arm capable of moving head 16 inmultiple directions during fabrication of structure 12, such that aresulting longitudinal axis (e.g., a trajectory) of structure 12 isthree-dimensional. Support 14 may alternatively embody an overheadgantry or a hybrid gantry/arm also capable of moving head 16 in multipledirections during fabrication of structure 12. Although support 14 isshown as being capable of 6-axis movements, it is contemplated that anyother type of support 14 capable of moving head 16 in the same or adifferent manner could also be utilized. In some embodiments, a drivemay mechanically couple head 16 to support 14, and include componentsthat cooperate to move portions of and/or supply power to head 16.

Head 16 may be configured to receive or otherwise contain a matrixmaterial. The matrix material may include any type of matrix material(e.g., a liquid resin, such as a zero-volatile organic compound resin, apowdered metal, etc.) that is curable. Exemplary resins includethermosets, single- or multi-part epoxy resins, polyester resins,cationic epoxies, acrylated epoxies, urethanes, esters, thermoplastics,photopolymers, polyepoxides, thiols, alkenes, thiol-enes, and more. Inone embodiment, the matrix material inside head 16 may be pressurized,for example by an external device (e.g., by an extruder or another typeof pump—not shown) that is fluidly connected to head 16 via acorresponding conduit (not shown). In another embodiment, however, thepressure may be generated completely inside of head 16 by a similar typeof device. In yet other embodiments, the matrix material may begravity-fed into and/or through head 16. For example, the matrixmaterial may be fed into head 16, and pushed or pulled out of head 16along with one or more continuous reinforcements. In some instances, thematrix material inside head 16 may need to be kept cool and/or dark inorder to inhibit premature curing or otherwise obtain a desired rate ofcuring after discharge. In other instances, the matrix material may needto be kept warm for similar reasons. In either situation, head 16 may bespecially configured (e.g., insulated, temperature-controlled, shielded,etc.) to provide for these needs.

The matrix material may be used to coat any number of continuousreinforcements (e.g., separate fibers, tows, rovings, socks, and/orsheets of continuous material) and, together with the reinforcements,make up a portion (e.g., a wall) of composite structure 12. Thereinforcements may be stored within (e.g., on one or more separateinternal spools—not shown) or otherwise passed through head 16 (e.g.,fed from one or more external spools—not shown). When multiplereinforcements are simultaneously used, the reinforcements may be of thesame material composition and have the same sizing and cross-sectionalshape (e.g., circular, square, rectangular, etc.), or a differentmaterial composition with different sizing and/or cross-sectionalshapes. The reinforcements may include, for example, carbon fibers,vegetable fibers, wood fibers, mineral fibers, glass fibers, metallicwires, optical tubes, etc. It should be noted that the term“reinforcement” is meant to encompass both structural and non-structuraltypes of continuous materials that are at least partially encased in thematrix material discharging from head 16.

The reinforcements may be exposed to (e.g., at least partially coatedwith) the matrix material while the reinforcements are inside head 16,while the reinforcements are being passed to head 16, and/or while thereinforcements are discharging from head 16. The matrix material, dryreinforcements, and/or reinforcements that are already exposed to thematrix material may be transported into head 16 in any manner apparentto one skilled in the art. In some embodiments, a filler material (e.g.,chopped fibers) may be mixed with the matrix material before and/orafter the matrix material coats the continuous reinforcements.

One or more cure enhancers (e.g., a UV light, an ultrasonic emitter, alaser, a heater, a catalyst dispenser, etc.) 18 may be mounted proximate(e.g., within, on, or adjacent) head 16 and configured to enhance a curerate and/or quality of the matrix material as it is discharged from head16. Each cure enhancer 18 may be controlled to selectively exposeportions of structure 12 to energy (e.g., UV light, electromagneticradiation, vibrations, heat, a chemical catalyst, etc.) during theformation of structure 12. The energy may increase a rate of chemicalreaction occurring within the matrix material, sinter the material,harden the material, or otherwise cause the material to cure as itdischarges from head 16. In the depicted embodiments, cure enhancer 18includes multiple LEDs (e.g., 6 different LEDs) that are equallydistributed about a center axis of head 16. However, it is contemplatedthat any number of LEDs or other energy sources could alternatively beutilized for the disclosed purposes and/or arranged in another manner(e.g., unequally distributed). The amount of energy produced by cureenhancer 18 may be sufficient to cure the matrix material beforestructure 12 axially grows more than a predetermined length away fromhead 16. In one embodiment, structure 12 is completely cured before theaxial growth length becomes equal to an external diameter of thematrix-coated reinforcement. In another embodiment, only an outer shellof structure 12 is cured before the axial growth length becomes equal toan external diameter of the matrix-coated reinforcement.

The matrix material and/or reinforcement may be discharged from head 16via at least two different modes of operation. In a first mode ofoperation, the matrix material and/or reinforcement are extruded (e.g.,pushed under pressure and/or mechanical force) from head 16, as head 16is moved by support 14 to create the 3-dimensional trajectory within alongitudinal axis of structure 12. In a second mode of operation, atleast the reinforcement is pulled from head 16, such that a tensilestress is created in the reinforcement during discharge. In this mode ofoperation, the matrix material may cling to the reinforcement andthereby also be pulled from head 16 along with the reinforcement, and/orthe matrix material may be discharged from head 16 under pressure alongwith the pulled reinforcement. In the second mode of operation, wherethe matrix material is being pulled from head 16 with the reinforcement,the resulting tension in the reinforcement may increase a strength ofstructure 12 (e.g., by aligning the reinforcements, inhibiting buckling,compressing the matrix, ensuring distributed reinforcement loading,etc.), while also allowing for a greater length of unsupported structure12 to have a straighter trajectory. That is, the tension in thereinforcement remaining after curing of the matrix material may actagainst the force of gravity (e.g., directly and/or indirectly bycreating moments that oppose gravity) to provide support for structure12.

The reinforcement may be pulled from head 16, as a result of head 16moving away from an anchor point 20. In particular, at the start ofstructure formation, a length of matrix-impregnated reinforcement may bepulled and/or pushed from head 16, deposited onto anchor point 20, andcured such that the discharged material adheres (or is otherwisecoupled) to anchor point 20. Thereafter, head 16 may be moved away fromanchor point 20, and the relative movement may cause the reinforcementto be pulled from head 16. It should be noted that the movement ofreinforcement through head 16 could be assisted (e.g., via internal headmechanisms), if desired. However, the discharge rate of reinforcementfrom head 16 may primarily be the result of relative movement betweenhead 16 and anchor point 20, such that tension is created within thereinforcement. It is contemplated that anchor point 20 could be movedaway from head 16 instead of or in addition to head 16 being moved awayfrom anchor point 20.

A controller 22 may be provided and communicatively coupled with support14, head 16, and any number of cure enhancers 18. Each controller 22 mayembody a single processor or multiple processors that are configured tocontrol an operation of system 10. Controller 22 may include one or moregeneral or special purpose processors or microprocessors. Controller 22may further include or be associated with a memory for storing data suchas, for example, design limits, performance characteristics, operationalinstructions, tool paths, and corresponding parameters of each componentof system 10. Various other known circuits may be associated withcontroller 22, including power supply circuitry, signal-conditioningcircuitry, solenoid driver circuitry, communication circuitry, and otherappropriate circuitry. Moreover, controller 22 may be capable ofcommunicating with other components of system 10 via wired and/orwireless transmission.

One or more maps may be stored in the memory of controller 22 and usedduring fabrication of structure 12. Each of these maps may include acollection of data in the form of lookup tables, graphs, and/orequations. In the disclosed embodiment, the maps may be used bycontroller 22 to determine the movements of head 16 required to producethe desired size, shape, and/or contour of structure 12, and to regulateoperation of cure enhancers 18 (and/or other components of system 10) incoordination with the movements.

An exemplary head 16 is disclosed in detail in FIGS. 2 and 3. Head 16may include, among other things, a matrix reservoir 24 and a nozzle 26removably and fluidly connected to matrix reservoir 24. In this example,nozzle 26 is single path nozzle configured to discharge compositematerial having a generally circular cross-section. The configuration ofhead 16, however, may allow nozzle 26 to be swapped out for anothernozzle (not shown) that discharges composite material having a differentshape (e.g., a tubular cross-section, a linear cross-section, abox-shaped cross-section, a triangular cross-section, etc.).

An internal volume of matrix reservoir 24 may communicate with nozzle 26via a central opening 28. In the disclosed embodiment, matrix reservoir24 has a generally circular cross-section, and tapers radially inward tocentral opening 28. A size (e.g., diameter and/or height) of matrixreservoir 24 may be sufficient to hold a supply of matrix materialnecessary for wetting reinforcements passing through nozzle 26.

As shown in FIGS. 2 and 3, the matrix material is non-pressurized andallowed to move somewhat inside of matrix reservoir 24 during movementsof head 16. For example, when head 16 is in an upright or normalposition, the matrix material naturally flows toward and/or collects atcentral opening 28. At this location, the reinforcements passing throughnozzle 26 may readily be wetted and saturated with the matrix materialprior to discharge. However, when head 16 is tilted away from the normalposition, the matrix material may move away from central opening 28.Unless otherwise accounted for, it might be possible for thereinforcement passing through nozzle 26 to be undersaturated. For thisreason, a flop-guide 30 may be provided.

Flop guide 30 may be configured to move an in-head path of thereinforcement at a location upstream of nozzle 26 through the matrixmaterial, regardless of where the matrix material pools within head 16.Flop guide 30 may include, among other things, a guide portion 30 a, anda tether portion 30 b that moveably (e.g., flexibly) connects guideportion 30 a to another component (e.g., to an internal wall or endsurface of matrix reservoir 24) of head 16.

Guide portion 30 a may include, for example, a weighted eyelet, ring,hook, or another similarly shaped structure that at least partiallysurrounds the reinforcement, without substantially restricting passageof the reinforcement through head 16 in an axial direction. In oneembodiment, tether portion 30 b is a chain, a fiber, a rope, a cord(e.g., a bungee cord), or another similar tie that restricts movement ofguide portion 30 a. In another embodiment, tether portion 30 b is afixed device (e.g., spaced apart plates, grates, channels, etc.) thatallows guide portion 30 to move within a desired region. Tether portion30 b may allow guide portion 30 a to move radially within matrixreservoir 24 during tilting of head 16, but substantially inhibits axialmotion. Alternatively, tether portion 30 b allows guide portion 30 a tomove both radially and axially, at least to some degree, within matrixreservoir 24. It is contemplated that, in some embodiments, tetherportion 30 b may be omitted, and guide portion 30 a may be used aloneand without movement restriction by an associated tether, if desired.

INDUSTRIAL APPLICABILITY

The disclosed system and print head may be used to continuouslymanufacture composite structures having any desired cross-sectionalshape and length. The composite structures may include any number ofdifferent fibers of the same or different types and of the same ordifferent diameters, and any number of different matrixes of the same ordifferent makeup. Operation of system 10 will now be described indetail.

At a start of a manufacturing event, information regarding a desiredstructure 12 may be loaded into system 10 (e.g., into controller 22 thatis responsible for regulating operations of support 14 and/or head 16).This information may include, among other things, a size (e.g.,diameter, wall thickness, length, etc.), a contour (e.g., a trajectory),surface features (e.g., ridge size, location, thickness, length; flangesize, location, thickness, length; etc.), connection geometry (e.g.,locations and sizes of couplings, tees, splices, etc.), desired weavepatterns, weave transition locations, etc. It should be noted that thisinformation may alternatively or additionally be loaded into system 10at different times and/or continuously during the manufacturing event,if desired. Based on the component information, one or more differentreinforcements and/or matrix materials may be selectively installedand/or continuously supplied into system 10.

To install the reinforcements, individual fibers, tows, and/or ribbonsmay be passed through matrix reservoir 24, through extension guideportion 30 a, and through nozzle 26. In some embodiments, thereinforcements may also need to be connected to a pulling machine (notshown) and/or to a mounting fixture (e.g., to anchor point 20).Installation of the matrix material may include filling head 16 (e.g.,reservoir 24) and/or coupling of an extruder (not shown) to head 16.

The component information may then be used to control operation ofsystem 10. For example, the reinforcements may be pulled and/or pushedalong with the matrix material from head 16. Support 14 may alsoselectively move head 16 and/or anchor point 20 in a desired manner,such that an axis of the resulting structure 12 follows a desiredthree-dimensional trajectory. Cure enhancers 18 may be adjusted duringoperation to provide for desired curing conditions. Once structure 12has grown to a desired length, structure 12 may be severed from system10.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed system andprint head. Other embodiments will be apparent to those skilled in theart from consideration of the specification and practice of thedisclosed system and print head. It is intended that the specificationand examples be considered as exemplary only, with a true scope beingindicated by the following claims and their equivalents.

What is claimed is:
 1. A print head for an additive manufacturingsystem, comprising: a matrix reservoir configured to hold a supply ofmatrix; a flop guide located within the matrix reservoir and configuredto at least partially surround a continuous reinforcement passingthrough the matrix reservoir, the flop guide including: a guide portionthat engages the continuous reinforcement; and a tether portion thatmoveably connects the guide portion to another component of the printhead; and an outlet connected to an end of the matrix reservoirdownstream of the flop guide.
 2. The print head of claim 1, wherein theflop guide is configured to maintain a path of the continuousreinforcement passing through the matrix in the matrix reservoir duringtilting of the print head.
 3. The print head of claim 1, wherein thetether portion is flexible.
 4. The print head of claim 1, wherein thetether portion is one of a chain, a fiber, a rope, and a bungee cord. 5.The print head of claim 1, wherein the guide portion is one of aneyelet, a ring, and hook that is weighted.
 6. The print head of claim 1,wherein the tether portion is connected to at least one of an internalwall and an end surface of the matrix reservoir.
 7. The print head ofclaim 1, wherein the tether portion allows the guide portion to moveradially within the matrix reservoir during tilting of the print head.8. The print head of claim 7, wherein the tether portion inhibits axialmotion of the guide portion.
 9. The print head of claim 1, wherein thematrix reservoir tapers radially inward to a central opening of theoutlet.
 10. An additive manufacturing system, comprising: a print headconfigured to discharge a continuous reinforcement at least partiallycoated with a matrix, the print head including: a matrix reservoir; aflop guide located within the matrix reservoir and at least partiallysurrounding the continuous reinforcement, the flop guide being moveablytethered to another component of the print head; and an outlet connectedto an end of the matrix reservoir downstream of the flop guide; and asupport configured to move the print head during discharging, whereinthe flop guide is configured to maintain a path of the continuousreinforcement passing through the matrix in the matrix reservoir duringtilting of the print head by the support.
 11. The additive manufacturingsystem of claim 10, wherein the flop guide includes: a guide portionthat engages the continuous reinforcement; and a tether portion thatmoveably connects the guide portion to the another component of theprint head.
 12. The additive manufacturing system of claim 11, whereinthe tether portion is flexible and is one of a chain, a fiber, a rope,and a bungee cord.
 13. The additive manufacturing system of claim 11,wherein the guide portion is one of an eyelet, a ring, and hook that isweighted.
 14. The additive manufacturing system of claim 11, wherein thetether portion is connected to at least one of an internal wall and anend surface of the matrix reservoir.
 15. The additive manufacturingsystem of claim 11, wherein the tether portion allows the guide portionto move radially within the matrix reservoir during tilting of the printhead.
 16. The additive manufacturing system of claim 15, wherein thetether portion inhibits axial motion of the guide portion.
 17. Theadditive manufacturing system of claim 10, wherein the matrix reservoirtapers radially inward to a central opening of the outlet nozzle.
 18. Anadditive manufacturing system, comprising: a support; and a print headhaving a housing and being connected to move with the support andconfigured to receive a reinforcement that is free of liquid matrix anddischarge the reinforcement at least partially coated in the liquidmatrix, the print head including a flop guide configured to maintain apath of the reinforcement passing through the liquid matrix duringtilting of the print head by the support, wherein the flop guide ismoveable radially within the housing and restrained axially within thehousing by another component of the print head that is moveable relativeto the housing.
 19. The additive manufacturing system of claim 18,wherein the flop guide includes a guide portion that moves thereinforcement radially to a gravitationally lower position in the printhead while allowing relative axial motion of the reinforcement.